SOLUTION: if (-2,7) is the maximum point for the graph of y=-2x^2-4bx+k FInd the value of k?

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: if (-2,7) is the maximum point for the graph of y=-2x^2-4bx+k FInd the value of k?      Log On


   

Question 815097: if (-2,7) is the maximum point for the graph of y=-2x^2-4bx+k FInd the value of k?
Answer by josgarithmetic(39613) About Me  (Show Source):
You can put this solution on YOUR website!
Here is a start but not the full answer.

y=-2%28x%5E2%2B2bx-k%2F2%29
y=-2%28x%5E2%2B2bx%2Bb%5E2-b%5E2-k%2F2%29
y=-2%28%28x%2Bb%29%5E2-%28b%5E2%2Bk%2F2%29%29
highlight%28y=-2%28x%2Bb%29%5E2%2B2%28b%5E2%2Bk%2F2%29%29
This is after completing the square and is now in standard form. The vertex is at x=-b and y=2%28b%5E2%2Bk%2F2%29

You are essentially given that as a maximum, (-2,7) is the vertex, and now you will equate -2=-b and 7=2%28b%5E2%2Bk%2F2%29; and you clearly will find how to finish this.